Fix grpc api

Author: guohao

contrib/grpc-spring/src/test/java/com/salesforce/grpc/contrib/spring/GrpcServerHostEndToEndTest.java

@@ -49,7 +49,7 @@ public void serverIsRunningAndSayHelloReturnsExpectedResponse() throws Exception
 
         ManagedChannel channel = ManagedChannelBuilder
                 .forAddress("localhost", grpcServerHost.getPort())
-                .usePlaintext(true)
+                .usePlaintext()
                 .build();
 
         GreeterGrpc.GreeterFutureStub stub = GreeterGrpc.newFutureStub(channel);

contrib/grpc-spring/src/test/java/com/salesforce/grpc/contrib/spring/GrpcServerHostInProcessEndToEndTest.java

@@ -52,7 +52,7 @@ public void serverIsRunningAndSayHelloReturnsExpectedResponse() throws Exception
 
         ManagedChannel channel = InProcessChannelBuilder
                 .forName(SERVER_NAME)
-                .usePlaintext(true)
+                .usePlaintext()
                 .build();
 
         GreeterGrpc.GreeterFutureStub stub = GreeterGrpc.newFutureStub(channel);

demos/grpc-java-contrib-demo/time-client-demo/src/main/java/com/salesforce/servicelibs/timeclient/TimeClient.java

@@ -35,7 +35,7 @@ public static void main(String[] args) throws Exception {
         Channel channel = ManagedChannelBuilder
                 .forTarget(abstractName)
                 .nameResolverFactory(StaticResolver.factory(new InetSocketAddress(host, port)))
-                .usePlaintext(true)
+                .usePlaintext()
                 .build();
 
         // Create a CompletableFuture-based stub